The effect of dehydration and rehydration with a high potassium beverage on muscular strength in collegiate males
Introduction: Dehydration has been shown to impact both health and aerobic exercise performance, with less research examining the impact of dehydration on muscular strength. Rapid weight loss via dehydration is a common practice in several weight class sports dealing with muscular strength and power. Exercisers may also unintentionally begin a resistance training session in a dehydrated state as a result of hot environmental conditions or failure to restore fluid balance following previous activity, possibly inhibiting performance. Most rehydration strategies have focused on the inclusion of sodium in a beverage to restore plasma volume, while less have considered the role of potassium. Purpose: The purpose of this study was to determine the impact of exercise dehydration and rehydration with a commercially available high potassium sports drink versus a sugar water placebo on strength measures. Methods: Ten college-age resistance trained males were recruited for this study. Participants came to the lab on two occasions for different treatment conditions in a randomized crossover design. Treatment order was counterbalanced for participants. At each visit, participants were asked to dehydrate 3% of body mass for up to 120 minutes via low intensity cycling in a heated chamber, (40 deg C [104 deg F], 60% RH) followed by a rehydration protocol. The rehydration protocol consisted of a total fluid volume in an amount equal to body mass lost during dehydration (1 LÃ Â·kg-1). Half of the rehydration fluid volume consisted of the test beverage, with the subsequent half consisting of plain water. Rehydration fluids were given at thirty minute intervals for two hours for all subjects. Tested beverages were a commercially available high potassium sports drink and sugar water placebo matched for carbohydrate content. Strength measures consisted of dominant knee extensor and flexor peak torque, leg fatigability and one-repetition maximum bench press. Leg peak torque was measured with an isokinetic dynamometer at three different speeds, while fatigability was measured via a 50-repetition maximal effort test. Strength measures were assessed for participants before dehydration, after dehydration, and after rehydration. Results: The dehydration protocol resulted in a mean reduction of 2.82 Ã Â± 0.1% of body mass, which remained 0.8 Ã Â± 0.1% below euhydration levels following each rehydration protocol. A significant decline was observed in bench press performance and knee extensor isokinetic peak torque at 60 degÃ Â·sec-1 and was not fully recovered with rehydration (p < 0.05). Average torque during the 50-repetition test also significantly declined following dehydration but was recovered with rehydration (p < 0.05). The high potassium sports drink was not significantly different from the sugar water placebo in its ability to restore performance or hydration status. Neither drink resulted in complete rehydration. Conclusion: Exercise dehydration reduced maximal bench press performance and dominant leg extensor peak torque at slower isokinetic speeds, which was not recovered after two hours of rehydration with either a high potassium sports drink or a sugar water placebo.